Patent GB-704604-A (GB)
Title: Lubricating grease
Filed: 1949-12-09
Abstract: A lubricating grease composition which is stable in the presence of moisture is prepared by forming an inorganic gel having a solid phase and a liquid phase, the liquid phase being lubricating oil, and applying a coating of a waterproofing material to the solid phase. The lubricating oil may be mineral lubricating oil or an oily natural or synthetic ester or a polyglycol.  The esters may be alkyl or at least aliphatic esters of dibasic acids such as phthalic, sebacic, malonic, succinic, glutaric, or adipic acid, or they may be esters of polyhydric alcohols such as glycols or glycerol with monobasic acids. Specific esters mentioned are ethyl hexyl sebacate, dimethyl or dioctyl phthalate, and triethylene glycol di-2-ethyl butyrate. The inorganic gel may be silica, ferric, hydroxide, alumina, aluminium hydroxide, thoria, titania, talc, bentonite, the siliceous earth known commercially as volclay, wetball-milled mica or vermiculite, wet ball-milled asbestos, graphite, magnesium oxide, calcium carbonate, and sodium chloride precipitated from acetone.  The gel may be formed as an aquagel, then the water displaced therefrom by a volatile liquid, and after further displacements with other liquids if necessary, the liquid phase is replaced by lubricating oil. Alternatively, the aquagel may be converted to an aerogel and the latter incorporated in the lubricating oil.  The water proofing material may be a polymerized hydrocarbon, a polymeric organo-silicon compound, an alkyd resin or a metal soap.  The polymerized hydrocarbon may be polymerized butadiene or polystyrene and may be incorporated by passing gaseous butadiene or styrene over the dry aerogel in a heated tube.  Alternatively styrene may be added to the lubricating oil and then, after the incorporation of the inorganic gel, the grease is heated to polymerize the styrene.  As another alternative, a chloroform solution of polystyrene may be added to the lubricating grease composition and the chloroform distilled off The alkyd resin employed as waterproofing material may be formed by esterifying polycarboxylic acids of corresponding acidogenic materials, particularly phthalic, maleic or succinic acids or their anhydrides, or tetra chloro-phthalic anhydride, with polyhydric alcohols such as glycerol, if desired in presence of fatty oils such as drying oils.  The polymeric organo-silicon compounds employed as waterproofing materials may be resinous silicones formed by the hydrolysis of amino silanes such as alkoxy aminosilanes, particularly ditertiary butoxy aminosilane, or of alkyl silicon chlorides, or by the dehydration of dialkyl-silane diols.  Thus the aminosilane may be added to the lubricating oil, preferably together with a little water, before the incorporation of the inorganic gel.  Finished greases containing such polymeric organo-silicon compounds are preferably baked at about 105 DEG C. for an hour or so before use. The metal soap specified as waterproofing agent is aluminium stearate.  The grease compositions may also be passed through a colloid mill before use.  The lubricating grease compositions may contain additional ingredients such as oxidation inhibitors, tackiness agents, extreme pressure additives and surface active agents.  The preparation of a number of grease compositions is described in detail.  The non - aqueous compositions of Specifications 672,650 and 672,651 are disclaimed and U.S.A. Specification 2,260,625 also is referred to.